The major aim of this project is to characterize immunoglobulin responses in helminth infections (primarily filariasis and schistosomiasis) with emphasis on IgE production, regulation and modulation. Highly sensitive radioimmunoassays have been developed to detect and quantitate both IgG and IgE antibodies. IgE was then determined in various clinical forms of filariasis (chronic pathology, microfilaremia, tropical pulmonary eosinophilia) and schistosomiasis (actue and chronic). In addition, individuals living in endemic areas but without clinical disease are also being simultaneously studied to understand their defense mechanisms. Immediate hypersensitivity (IgE) responses have been found to be modulated by IgG blocking antibody. IgG subclasses are being studied in an attempt to define the carrier of blocking activity. Finally, qualitative characterization of IgE responses in different disease states are being carried out in an attempt to define the allergies to which these responses are directed ("fingerprinting") in order to correlate immune recognition with disease or protective state. This would, in addition, provide information about antigens with better specificity in immunodiagnosis or epidemiologic studies.